fuel pressure issues

[ratty]

i'm running a vented fuel cell, to mechanical high volume fuel pump, to dead-head fuel regulator, to fuel pressure gauge, to in-line fuel filter, to holly HP4150... not the best set-up/sequence, but has been working fine for about 5 years...

then i started having stalling problems recently, with fuel overpowering my needle 'n seat assemblies and overflowing through the vent tubes...

replaced my fuel regulator, since my needle 'n seat assemblies weren't that old, and still a problem...

then replaced my floats, and needle 'n seat assemblies... problem seems to have been cured, but still having a fuel pressure issue... my fuel pressure, which i normally have set for around 4-3/4 psi, am having a hard time setting it under 5 psi... the adjuster on my regulator is adjusted so far out (up) it's almost unscrewed... showing 5 psi at the minimum...

but here's the weirdest part, when i shut my engine off, the fuel pressure creeps up to around 7 psi... not sure how that can happen, and it may be a symptom of what was originally wrong with it... not too eager to drive around and have it stall in a bad place (i know Holley's don't like much fuel pressure).. the pressure NEVER lowers like it used to when shut-off, it just stays pegged at around 7 psi, even after several days

fuel looks clean, filter is clean...

thinking maybe i was shipped the wrong regulator (it's a typical Holley regulator), which would account for me being unable to adjust it properly... but still doesn't account for the pressure creep AFTER engine shutoff...

has anyone ever encountered this issue?

i've had plans to add a bypass regulator and return line, which would probably alleviate excess pressure issues, but i would rather find out what's causing it in the first place... someone mentioned it could be an issue with my fuel pump, and a pressure release valve in it... i didn't realize there was a pressure release valve in it... gonna take it apart and see if there's anything weird going on it it, but it's just stabbing in the dark

not into spending money on a new fuel pump just guessing what may be wrong...

any ideas would be greatly appreciated... thanks!

[MR P-BODY]

In thhe mech fuel pump the spring is the so called relief valve... the diaphragm wont stroke
when it over rides the spring pressure.. other wise all thats in it is 2 check valves and the
diaphragm.... where is the fuel pressure gauge and is it a oil filled gauge... the oil filed ones
heat up and push back on the pressure tube inside and give bogus readings... if its oil filled
just drain the oil out of it... holley needle and seats will handle up to 7.5 psi if you use a good
gauge... right now with the gauge/presure climbing thats most likely just the fuel heating up
with no place to go so the pressure climbs on the gauge

[ratty]

In thhe mech fuel pump the spring is the so called relief valve... the diaphragm wont stroke
when it over rides the spring pressure.. other wise all thats in it is 2 check valves and the
diaphragm.... where is the fuel pressure gauge and is it a oil filled gauge... the oil filed ones
heat up and push back on the pressure tube inside and give bogus readings... if its oil filled
just drain the oil out of it... holley needle and seats will handle up to 7.5 psi if you use a good
gauge... right now with the gauge/presure climbing thats most likely just the fuel heating up
with no place to go so the pressure climbs on the gauge

not an oil filled gauge, and it's right after the regulator, before the carb...

wouldn't the pressure drop down to zero after time, if it's a hot fuel issue? i've never seen that before... usually when i shut my engine off, the pressure drops slowly down to zero in a few minutes... now it climbs up and stays there... maybe i have a gauge problem as well

thanks for the info... i guess opening up my fuel pump will prove fruitless... thought maybe because i have my filter after my regulator, or rather after my pump and regulator, i might've gotten some debris in my pump, causing the issue

[MR P-BODY]

You should have a filter before the pump to keep the trash out of the pump and regulator...
when the engine cools down it will drop some but if its all sealed (like it should be) then
it will drop a little... if it dropped to 0 before it was leaking past something(needle and seat or a
check in the pump which I doubt .. they have rebuilt kits for those regulators if you want to...
if you havent ever had the gauge calibrated you might want to have it checked

[Barry Donovan]

you described all my cars with mechanical pumps.

5 years is a long lucky run. the mech pumps life span, (in maine anyway.)

I am posting about the monojet as a modern example..the way the fuel runs fixes all of the old problems. I even found a regulator is not even needed when the return is reduced in the right spot.

emulsifying is an act approaching subatomics. A chain of anything can set it off for days, creeping. The return to tank kills that too.

could be as simple as the type of gaskets in the carb, in the fuel pump..even the fuel filter can make a weird thing happen if it aint right in materials.

your post is exactly why I am doing what I am doing.

does the carb have a vent? a vent can? tank vent?

the old spewing out the back gas cap days are done.

[ratty]

You should have a filter before the pump to keep the trash out of the pump and regulator...
when the engine cools down it will drop some but if its all sealed (like it should be) then
it will drop a little... if it dropped to 0 before it was leaking past something(needle and seat or a
check in the pump which I doubt .. they have rebuilt kits for those regulators if you want to...
if you havent ever had the gauge calibrated you might want to have it checked

yeah, i'm guessing my needle 'n seats were quite worn, hence the overflow... and like you say, hence the leakage.. the gauge could be suspect (i never thought of gauges 'breaking', that is until my mechanical tranny gauge decided to stop working altogether)

[ratty]

you described all my cars with mechanical pumps.

5 years is a long lucky run. the mech pumps life span, (in maine anyway.)

I am posting about the monojet as a modern example..the way the fuel runs fixes all of the old problems. I even found a regulator is not even needed when the return is reduced in the right spot.

emulsifying is an act approaching subatomics. A chain of anything can set it off for days, creeping. The return to tank kills that too.

could be as simple as the type of gaskets in the carb, in the fuel pump..even the fuel filter can make a weird thing happen if it aint right in materials.

your post is exactly why I am doing what I am doing.

does the carb have a vent? a vent can? tank vent?

the old spewing out the back gas cap days are done.

oddly enough i've never had fuel pump issues on any of my cars (all mechanical)... the worst issue i've ever had was with the Edelbrock 6-valve pumps, the top cover is made out of cheese, and i would invariably always overtighten it when working on them, and then they would seep... nothing bad, just a dirt collector (gave up on those, been happily running a Carter Comp Series pump since)